In a conventional exhaust heat recovery system using a Rankine cycle, because super-cooling degree of operating fluid (hereinafter, referred to as refrigerant) varies during an operation caused by variation of outside air temperature or by fluctuation of condensation capacity of a condenser, a problem has occurred that efficiency of a refrigerant pump decreases. In order to solve this problem, an outlet side of the refrigerant pump and an inlet side of the condenser are communicated together through a bypass passage, and respective open/close valves are also provided at a high pressure side and a low pressure side of the bypass passage; thereby, by suitably opening or closing the open/close valve depending on the super-cooling degree at the outlet side of the condenser, the encapsulated amount of the refrigerant in the Rankine cycle has been controlled (for example, refer to Patent Document 1 and Patent Document 2).